Reusable auto injectors which can be loaded with a container subassembly, such as a syringe, are known in the prior art. U.S. Pat. No. 5,599,309 discloses an auto injector for use with proprietary syringes. That prior art discloses a device comprising a drive member that receives the rear end of a plunger of a syringe and a trigger for releasing the drive member such that a medicament can be injected. Drawbacks are that the needle is exposed outside the device and visible to the user after the device has been removed from the injection site and that the re-loading is complicated and time consuming.
Further, a number of devices are arranged with medicament delivery member covers that are capable of covering a medicament delivery member, such as an injection needle, before and after a dose delivery.
Some of these devices are arranged with springs that urge the medicament delivery member cover in the proximal direction, and while most devices have a locking function on the medicament delivery member cover after dose delivery, quite a number of devices have their medicament delivery member covers movable before dose delivery after a protective cap or the like has been removed. This increases the risk of accidental injuries because the medicament delivery member cover may be unintentionally pushed in a distal direction, exposing the medicament delivery member. Also if the device is dropped on a hard surface, the medicament delivery member risks being damaged.
The patent application WO 2010/023481 discloses a medicament delivery device provided with a medicament delivery member cover that is lockable before dose delivery. The medicament delivery member cover is held in a locked state by a torsion spring exerting a turning force on the shield in relation to the housing of the device. In order to activate the device a user has to turn the medicament delivery shield against the force of the torsion spring and at the same time press the proximal end of the medicament delivery member cover against a dose delivery site. This operation is not ideal in a user perspective, since it is not intuitive in what direction the shield should be turned and it may be quite awkward to turn the shield when performing e.g. a penetration sequence.
Also, it is not the torsion spring that performs the locking action after the device has been withdrawn from the dose delivery site, but other springs. This is a disadvantage since a common aim when designing medicament delivery devices is to reduce the number of components, and in particular force elements acting inside the device.
There is thus room for improvements for this kind of medicament delivery devices.